Annealing furnace



March 17, 1942. c. B. HOAK 2,276,97 V

ANNEALING FURNACE Filed Sept. 8, 1941 2 Sheets-Sheet 1.

INVEHTO B March 17, 1942.

c. B. HOAK 2,276,971

ANNEALING FURNACE Filed Sept. 8, 1941 -2 Sheets-Sheet 2 Patented "Mar. [17, 1942 a ANNEALING FURNACE Clarence B. Hoak, Steubenville, Ohio Application September a, 1941, Serial No. 410,014

12 Claims.

My invention relates to annealing furnaces and constitutes an improvement upon the disclosure of my Patent No. 2,255,617, dated September 9, 1941.

One object of this invention is to provide an annealing furnace which includes means for supplying heat to material being annealed, both a by radiation and by convection.

Another object of my invention is to provide a method and a means for more effectively controlling the amount of heat applied to an annealing box or material being annealed, at various points in the furnace, whereby the work is not unduly heated at some points as compared to other points, and whereby greater economy in fuel consumption can be obtained than in various other forms of annealing furnaces.

Still another object of my invention is to provide a means and a method whereby burner flames can be directly introduced into the chamber that contains the usual sheet-metal muflie or annealing box, and so controlled that they will not impinge directly against the mufile or box which encloses the material to be annealed, but will be controlled in such manner that while they will be directly exposed to the muflle or annealing box, the deleterious effect of direct impingement on the box is avoided, and also accurate control mufile or annealing box to prolonged action of open flames.

In the accompanying drawings, Figure 1' is a vertical sectional view through a furnace embodying my invention; Fig. 2 is a view taken on the line II-II of-Figfl; Fig. 3 is another sectional view of a portion of the structure of Fig. 2; Fig. 4 shows a modification of the structure of Fig. 1, and Fig. 5 is a view taken on the line VV of Fig. 4.

As shown in the drawings, the invention is applied to a furnace for annealing coils of strip steel or the like, but the principal features of the invention are applicable also to the annealing of other objects, including stacks of sheets which are enclosed in an ordinary annealing box of rectangular form. f

- The furnace is shown as placed upon a foundation or supporting base 4 containing a flue 5 that leads to a stack (not shown). Upon the foundation 4 is placed a base 6 of suitable brickwork, having a passageway la that communicates with the flue 5 and which is provided with a series of small, laterally-extending passageways 1 distributed throughout its length.; Also this base is provided with vertically-extending passages 8 and 9 that communicate with the single long passageway la as indicated more clearly in Fig. 2.

The furnace is of the portable hood type and comprises the usual external metal framework of structural members In and l I and plates 12, all suitably secured together by welding or otherwise, lifting ears l3 being provided at the top for moving the furnace from one location to another. The furnace is lined with the usual brickwork l4. Shown more clearly in Fig. 3, the sidewalls of the furnace have channel-like passageways l5 formed vided which is of similar arrangement and method of operation to that described in'detail in my said patent. This apparatus comprises upper headers 18 communicating through 'a' seriesof conduits 19 with the interior of the furnace, and lower headers 20 communicating with the furnace, through conduits 2|. The headers "and 20 have damper-controlled outlets 22 and 23 respectively that may be used as exhaust openings when desired. Motor-driven fans 25 are provided for forced circulation or movement of gases through a passageway 26 at eachside of the furnace, that connects the headers, and through the conduits l9 and 2| in either direction as may be desired, after the manner statedin my said patent. Doors 25a are provided in'the fan casings, to permit of forced exhaust to atmosphere ing burners 29, there being one burner 29 in each of the vertical passageways 15. Other fuel supply pipes 3| supply burners 32 that extend forwardly of and are located below the burners 29 but-at points forwardly of the radiating walls It.

Fuel supply pipes 33 and 34 and burners 35 and through which flow of gases takes place to the outlet 8. The circular wall of the, shell 40a. is

connected to theinner shell 40b by webs 33, to form passageways 42, the manic serving to enclose a coil 33 that is to be annealed. Gases can flow upwardly in the passageways 42 between the An important feature of my invention resides in the arrangement of the vertical passageways I5 and the burners 32 that extend to the inner sides of the radiating walls I8, with the exhaust or circulation of gases through the conduits 2| or exhaust thereof through the passageways 1.

Each vertical channel i5 has communication with a passageway 2| and a passageway 1.

According to one method of operation the furnace will be placed over the muille or annealing box 43 within which is contained the coil 39 or other work to be annealed. The burners 32 will be lit and a forced draft set up by the fans 25, to effect a flow of gases upwardly from the bumers 32 and backwardly through ports 4| that lead into the vertical channels l5. The gases will be drawn downwardly through forced draft by the pumps 25 and then exhausted-through the openings 22 of the upper headers II or, if the dampers 43 of said openings are closed and the dampers 4| of conduits I! open, the gases can be directed back into the upper part of the furnace.

As an alternative, the gasescan be exhausted from the'channels l5 through the passageways I by the fan 43 that is positioned in the flue 5. At any-rate, this forced draft will cause the flames of the burners 32 to be drawn into somewhat definite paths instead of spreading in an uncontrolled manner within the furnace chamber. This arrangement not only prevents the deleterious effect of having the flames impinge directly upon the metal annealing box or muille but permits of more effective control of heating at various zones throughout the furnace. For example, the bumers at midpoints between the ends of the furnace entirely or partially and the burners 29 lit. The radiant walls I5 will in the meantime have become heated and will radiate their heat against the sides of the muflie and their temperature may be maintained by the burners 29, during what may be termed the soaking period of the annealing operation. The burners 29 may be used without forced circulation, with perhaps slight natural draft past a damper 400 in the top of the furnace or in the flue 5, or forced draft may be provided by the fan 43 to draw heated gases through the vertical passageways 42 of the muffle and downwardly through the passageway 8, as well as drawing some of the heat through the horizontal passageways l to heat the lower side of the muflle.

The passages 8 and 9 at the bottom of the muiile are provided with damper plates or slides 43 that may cover more or less of these passages are caused to flow to different parts of the furnace under suctional force of fan 43.

Slide dampers 50 and 5| are provided in each of 'the vertical channels l5. With slide dampers 5|) closed and dampers 5| open, suctional force by the fans 25 through the manifolds 20 will cause a flow of heated gases from the burners 32, upwardly through the passageways 42, down through the well and openings 3 and 3, and through the passageways 1 and conduits 2| to the manifold II and into the upper part of the furnace through the conduits l3. Also, by opening the dampers c flow of these gases can be had over the top and outer sides of the muiiie.

The dampers 5| will ordinarily be closed and the dampers opened, when the heat from bumers '32 is being drawn through the openings 4| and down the passageways 5 to the manifolds 23. I Circulation of heating gases from the burners 35' and 33 can be effected by closing the dampers 53 and operating the fans 25 in a direction to create suction through the conduits 2|, in which case the heated gases would be drawn from the top of the furnace to the lower ends of the passageways 42, thence upwardly and then downwardly through the wells 3'! and the passageways l, the circulated gases being discharged through Is. In this case also the dampers 430 can be opened to permit of the flow of the heated gases from the top of the furnace to thewell 31. If

desired, the fans 25 need not be operated, but exhaust from the upper burners 35 and 33 effected by the-fan 43, through the passageways 42 and the well 3'! and also through the openings 4|, vertical channels l5 and passageways I, the dampers 400 this time being open or partly open, if desired.

The burners 35 can be utilized to heat the gases that pass through the conduits I! when the gases are being drawn through the conduits 2| to the manifolds ll, e

Referring now to Figs. 4 and 5, I show an arrangement wherein baflie members 54 are provided in front of the lowermost burners 55 that correspond to the burners 32, these burners 55 being also mounted in the fixed base 55, and therefore remaining in position when the furnace hood is removed from the base. Only one-half of the furnace is indicated, the other half being of identical form. This arrangement prevents directi impingement of these burner flames upon the initially heated the burners 32 may be shut off sides of the muflie even though the flames are projected with considerable force. When the flames are quite high, as during the initial heating stage, so that they extend above the upper ends of the bailles 54, the dampers 5| can be closed and the fans 25 operated to draw the hot gases through the ports 4| as in the case of Fig; 1. As shown more clearly in Fig. 5, these baflles 54 are of generally channel form placed in upright position, but it will be understood that a single baiile plate so as to control the extent to which hot gases 54 could be provided. The baflles 54 may be made I of carborundum or other material which is highly refractory and has considerable heat-radiating capacity, so that they will radiate heat to the lower portion of the muille.

After the initial heating stage, the burners 55 can be turned down somewhat and a considerable part of the heat therefrom caused to be transmitted through and radiated from the innermost,

or front sides of the baffles 54 to'the annealingbox. Also, the burners 29 will be lit to supply heat for the heat-radiating wall l6. At this time hot air currents or forced draft may be set up within the furnac either by the fan 43'or by the fans 25, or both; or natural draft can be had through the flue or past the dampers 400.

I claim as my invention:

7. Annealing apparatus comprising a chamber, heat-radiating walls within the chamber and having their front sides exposed to the workreceiving space, means for supplying burner flames at said front sides, main furnace walls disposed at the rear sides of the radiating walls and in spaced relation thereto, there being openings for communication between the work-re- 1. Annealing apparatus comprising a chamber,

heat-radiating surfaces within the chamber and each having one side exposed to the work-receiving space, means for supplying burner flames at points between said sides and the said space, and means for applying a suctional force at the vicinity of the flames, to cause them to remain in a plane adjacent to said sides.

2. Annealing apparatus comprising a chamber, heat-radiating surfaces within the chamber and each having one side exposed to the work-receiving space, means for supplying burner flames at points between said sides and the said space, and means for applying a suctional force at the vicinity of the flames, in such direction that the major portion of the flames will be drawn along paths in parallelism with the said sides.

3. Annealing apparatus comprising a chamber, heat-radiating walls within the chamber and having their front sides exposed to the workreceiving space, passageways formed at the rear sides of of the said walls and having communication with the said space, through openings at the upper portions of said walls, means for supplying burner flames at the front sides of said walls, and means for supplying burner flames to the rear sides of the walls,

4. Annealing apparatus comprising a chamber, heat-radiating walls within the chamber and having their front sides exposed to the workreceiving space, passageways formed at the rear sides of the said walls and having communication with the said space, through openings at the upper portions of said walls, means for supplying burner flames at the front sides of said walls, means for supplying burner flames to the rear sides of the walls, and means for producing a down draft in the said passageways.

5. Annealing apparatus comprising a chamber, heat-radiating walls within the chamber and having their front sides exposed to the workreceiving space, passageways formed at the rear sides of the said walls and having communication with the said space, through openings at the upper portions of said walls, means for supplying burner flames at the front sides of said walls, means for supplying burner flames to the rear sides of the walls, and means for producing ,a down-draft in the said passageways, the said openings being in approximately vertical alignment with the first-named burners.

6. Annealing apparatus comprising a chamber, heat-radiating walls within the chamber and paths leading from said points and through the said openinss.

ceiving space and the space between the r-adiat ing and furnace walls, above the burner flames, and means for creating a suctional force through said openings, from the work-receiving space to the rear sides of the radiating walls.

8. Annealing apparatus comprising a chamber, heat-radiating walls within the chamber and having their front sides exposed to the work-receiving space, means for supplying burner flames at said front sides, main furnace walls disposed at the rear sides of the radiating walls and in spaced relation thereto, there being openings for communication between the work-receiving space and the space between the radiating and furnace walls, above the burner flames, means for creating a suctional force through said openings, from the work-receiving space to the rear sides of the radiating walls, and burners disposed between the radiating walls and the main furnace walls, adjacent to the lower end thereof.

9. Annealing apparatus comprising a cham-' ber, heat-radiating surfaces within the chamber and each having its front side exposed to the work-receiving space, means for supplying burner flames at points between said sides and said space, bafiie walls positioned between said points and said space, and means for supplying burner flames to the rear sides of said heat-radiating surfaces.

10. Annealing apparatus comprising a chamber, heat-radiating surfaces within the chamber and each having its front side exposed to the work-receiving space, means for supplying burner flames at points between said sides and said space, bafiie walls positioned between said points and said space, and being of less height than the said heat-radiating walls, and means for applying a suctional force to the flames in such direction that the heated gases thereof will be drawn into the ..spaces between the rear sides of the heat-radiating surfaces and the adjacent chamber wall.

11. Annealing apparatus comprising a heating chamber, means for supplying burner flames to that face of one of the chamber walls which is exposed to the annealing space within the cham-- ber, means for directing the flames in paths parallel to the said face of the wall, and means for thereafter directing portions of the hot gases from the said paths to paths along the opposite face of the wall.

l2. Annealing apparatus comprising a chamber, means for supplying burner flames to that face of a furnace wall whichis exposed within the chamber, means for directing the flames in paths parallel to the said face of the wall, means for directing portions of the hot gases from the said paths to paths along the opposite face of the wall, and means for supplying other heating gases at the said opposite face of the wall, to

maintain the wall at such temperature that there will be a substantial amount of heat radiatin therefrom into the said chamber.

CLARENCE B. HOAK. 

